Radio communication systems that utilize polling to establish communications are well known. An example is a cellular telephone system, in which a fixed transmitter network polls for a portable unit for which there is an incoming call, after which the called portable unit responds to establish two-way communications. Another example is a radio paging system that utilizes acknowledge-back pagers.
An "ack-back" pager employs a low-power transmitter that can transmit an acknowledgment response identifying the pager whenever a poll comprising an address specifically assigned to the pager is sent from a high-power fixed communication unit and received by the pager. To avoid communication collisions among responding pagers, the poll can also contain information that controls each pager to respond at a specific time, or on a specific communication channel. In addition, the ack-back transmitter transmits at a low bit rate, e.g., 100 bits per second, and the fixed communication unit utilizes narrow bandwidth, highly sensitive receivers to compensate for the low power of the ack-back transmitter, i.e., to help balance inbound and outbound transmission range.
A problem can result in a large ack-back communication system due to the low bit rate of the ack-back transmissions compared to the much higher bit rate, e.g., 2400 bits per second, utilized for the poll transmissions from the fixed communication unit. The problem arises when communication traffic increases to a point at which there is insufficient ack-back channel capacity to handle the volume of acknowledgment responses required, thereby significantly delaying poll response.
Thus, what is needed is a method and apparatus for increasing the volume of acknowledgment responses that can be transmitted in an ack-back communication system. A method and apparatus is needed that does not require additional ack-back channels or a utilization of a higher bit rate on the ack-back channels.